The DITA
1.3 source files of the specification come from OASIS and have not
been modified by us, except for a few, very minor changes in
dita-1.3-specification-technicalContent.ditamap, the root
map (excluded some useless booktitlealt when
platform="external-publishing-engine", un-commented out
indexlist, etc).

RenderX XEP requires adding
-Xmx2048m(which means: set the maximum size of the heap
to 2Gb) to its Java™ command-line in order to be able to
convert the spec to PDF. Apache FOP also requires
adding -Xmx2048m to its Java™ command-line in order to be
able to convert the spec to PDF. There is nothing special to do for XMLmind XSL-FO Converter,
for which the default memory setting of the Java™ runtime
(the maximum size of the heap is 64Mb) is fine.